8x=21x^2

Solution for 8x=21x^2 equation:

8x=21x^2

We move all terms to the left:

8x-(21x^2)=0

determiningTheFunctionDomain
-21x^2+8x=0

a = -21; b = 8; c = 0;
Δ = b2-4ac
Δ = 82-4·(-21)·0
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-8}{2*-21}=\frac{-16}{-42}
=8/21
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+8}{2*-21}=\frac{0}{-42}
=0
$